Re: [pygame] Limited Range?

[James Paige <Bob@xxxxxxxxxxxxxxxxxxx>]

A quick test with the timeit module suggest that the ** operator is not 
slower.

x*x and x**2 are exactly the same speed.

However, you are correct that x**0.5 is a slow operation.
raising something to the power of 0.5 is the same as taking its square 
root

x**0.5 is the same as math.sqrt(x)

Here is how I would write the distance check:

def is_in_range(enemy, tower):
  return (enemy.x-tower.x)**2 + (enemy.y-tower.y)**2 <= tower.range**2

---
James Paige


On Tue, Nov 03, 2009 at 09:24:50PM -0500, Michael George wrote:
> If you find this is too slow, you'll get much better performance by 
> removing the **'s, they're quite slow compared to other arithmetic.  Use 
> x*x instead of x**2 and square both sides of the inequality to remove 
> the **0.5.
> 
> P.F.C. wrote:
> >I'm not getting the attachment but this might help.
> >
> >If your doing range as a circle with radius = r then:
> >
> >if ((enemy.x-tower.x)**2+ (enemy.y-tower.y)**2)**0.5<=r: attack!!!
> >
> >basically, you'd be using Pythagorean theorem to find the distance to 
> >check if it attacks or not.
> >
> >Checking distances for every tower and every unit could become a 
> >bottle neck but would work.
> >
> >If you have performance problems you could also incorporate a grid.
> >When every unit moves it can do a check to see in what section of the 
> >map it is found in (ie, grid could have 10x10 tiles in each square) 
> >and you would only check the distance of creeps in the grids that are 
> >in range of the tower.
> >
> >One thing to keep in mind would be that in some cases you may be able 
> >to stop the iteration as soon as you find someone who is attackable 
> >(if the tower attacks random creeps) otherwise you just compare the 
> >distances of the creeps and sort.
> >
> >You may want to google for circle collision detection
> >
> >
> >-- Maranatha!
> >---------------------------------
> >PFC aka Fezzik aka GAB
> >
> >
> >On Tue, Nov 3, 2009 at 8:27 PM, Yanom Mobis <yanom@xxxxxxxxxxxxxx 
> ><mailto:yanom@xxxxxxxxxxxxxx>> wrote:
> >
> >    so, I wrote this tower defense game (zip archive attached) and I
> >    was wondering how I should go about implementing limited range
> >    (each tower can only shoot so far) in the code.
> >
> >
> >
> 
>